Monoarticular septic arthritis in a patient with juvenile rheumatoid arthritis under etanercept treatment.

A 7-year-old girl with polyarticular type juvenile rheumatoid arthritis (JRA) presented with acute onset of right hip pain with limited range of motion and fever within the past two days. She had received etanercept for more than one year. Percutaneous arthrocentesis was performed and showed a white blood cell count of 84150/μL in the synovial fluid, although the culture showed negative results. The fever and right hip pain completely resolved after antibiotic treatment. Herein, we report the first case of septic monoarthritis of JRA under etanercept treatment.